Keeping the Heat In
8 Upgrading windows and doors
8.1 Windows
8.2 Doors
UPGRADING WINDOWS
AND DOORS
Windows and doors can account for up to
25 percent of total house heat loss. This
chapter deals with upgrading or replacing
windows and doors to save energy.
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8.1 WINDOWS
There are a number of options for upgrading the
energy efficiency of your windows. Windows can
be repaired by servicing hardware such as latches,
cranks and locks or retrofitted with caulking and
weatherstripping or adding glazing and storm
windows. At times the best choice is total window
and frame replacement with new, high-performance
ENERGY STAR® qualified windows or inserts. If
the frames are still in good condition, inserts (i.e.
new sash and glazing units) can be a good option,
especially for homes with heritage status.
Keeping the Heat In ● Upgrading windows and doors
Figure 8-1 Casement window showing parts
and hardware
Figure 8-2 Double-hung window showing parts
and air-leakage paths
Sash
Header
(rough framing)
Drip cap or flash
Hinges
Interior trim
Exterior casing
Shim space
Window
frame
Upper sash
Wall (rough framing)
Glazing
Shim space
Lower sash
Window frame
Frame
Hinges, casement cranks,
handles, locks, latch plates,
sash balances, etc. that are
used to operate and lock the
window
8.1.1 Replacing glazing, sashes and windows
Properly installed energy-efficient windows make
homes more comfortable by reducing drafts
and increasing the temperature of the interior
side of the window, reducing condensation.
Energy-efficient windows will have many of the
following features:
• double-, triple- or even quadruple-glazing
• low-emissivity (low-E) glass
• inert gas, such argon or krypton in the sealed unit
• low conductivity or warm-edge spacer bars
• insulated frames and sashes
• good air tightness
If your inspection has revealed serious problems
with a window’s glazing, sash or the entire unit,
your best option will be to replace all or part of the
window.
Shim space
Exterior
sheathing
Drywall
Sill (rough
framing)
For example, if the glazing is only a single pane of
glass or is in poor condition, you can buy a new
sealed glazing window insert. If the frame is in poor
condition, it may be time to replace the unit.
8.1.2 Taking stock
Check each window for signs of damage: rot,
mould and/or staining on or around the window,
the condition of the glass, putty and paint,
weatherstripping and the operation and condition
of the hardware. Some windows may need only
minor air sealing work, while others require major
upgrading or even replacement. Check for air
leakage around the frame and at all movable joints.
Combine a visual inspection with a test using a
leak detector as described in Chapter 2, “How your
house works.”
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Keeping the Heat In ● Upgrading windows and doors
8.1.3 Condensation problems
Interior surface condensation and frosting are
common complaints. Sometimes the problem is
light fogging on some windows; at other times, there
may be persistent and heavy frost covering the glass.
Many homeowners buy new windows only to find
that the problem becomes worse because the old,
leaky windows actually helped to reduce humidity.
The new windows seal the house more tightly,
causing a rise in humidity. One solution is to reduce
humidity levels in the house.
For more information on moisture and
condensation, see Chapter 2, “How your house
works,” and Chapter 4, “Comprehensive air
leakage control.”
Figure 8-3 Where to caulk the joints of a
fixed window
Caulking
Shim space
Caulking
Shim space
Alternatively, you can increase the surface
temperature of the window and frame by adding
another layer of glazing. New energy-efficient
windows are the best solution.
When condensation forms between panes on nonsealed glazing units or storm windows, moist house
air has leaked past the inner pane and condensed
on the outer pane. Even dry houses can suffer from
this type of condensation problem. This problem is
common on second storeys where there is more air
being pushed out the window because of the stack
effect. The solution is to weatherstrip the inner sash
to prevent air leakage; make sure that the weep holes
on the storm windows, which allow water to escape,
are open to the outside.
If condensation occurs inside a sealed doubleglazed unit, the problem is best corrected by
replacing the glazing unit. Although some specialty
companies can refurbish sealed glazing units that
have failed, this is considered a temporary fix that
will not offer the same original energy efficiency.
Check to see if the window is still under warranty.
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8.1.4 Interior caulking
Window air leakage can be reduced by applying
a continuous bead of caulk around the window
trim where it meets the wall, at the mitred joints
of the trim, and between the trim and the frame
(see Figure 8-3). Make sure the caulk is intended
for indoor use (do not use exterior caulking
indoors), can be painted and is of good quality.
For more information about caulking products,
see Section 3.3, Air barrier materials.
If a window is particularly leaky and the trim can
be easily removed and re-installed, remove the trim,
add insulation and seal the gap before reapplying
the trim. If the gap is small, 6 mm (1/4 in.) or less,
insulating the gap followed by caulking may suffice.
Larger gaps may require either a backer rod with
caulking or low-expansion foam (see Figure 8-4).
Keeping the Heat In ● Upgrading windows and doors
Figure 8-4 How to seal behind the window trim
8.1.6 Weatherstripping
Weatherstrip windows around the sash to reduce air
leakage. If the windows do not have to be opened
and do not serve as emergency exits, they can be
locked and caulked. Where storm windows are installed, seal the inside window more tightly than the
outside window to reduce condensation problems.
TECHNICAL NOTE: Building codes
require that every bedroom have at least
one window that opens from the inside
to allow escape in case of emergency.
Be mindful of this requirement before
deciding to seal shut certain windows.
Drywall
Low-expansion
foam insulation
Frame
To further reduce air leakage, apply a layer of red
technical tape to cover the joint between the wall
and window frame. Ensure that the tape will be
hidden by the trim as it cannot be painted and red
adhesive may remain after excess tape is removed.
8.1.5 Exterior caulking
Exterior caulking is the last and weakest defence
against rain entering a wall from the outside. The
best defence against window and door wall leakage
includes the following two items:
roperly applied flashing (i.e. top window
• p
flashing is underneath the air barrier, while
side and bottom flashings are on top of the
air barrier)
• a properly detailed drainage plane
Caulking on the outside of a window should be
done only after interior sealing is complete. If the
exterior is caulked first, it can trap warm, moist air
in the wall, which over time, can damage the wall.
Many types of weatherstripping are available.
Table 3-4 lists some of the more common varieties
of weatherstripping, though it is certainly not an
exhaustive list. Try to visit a window and door
supplier that stocks a wide variety of original
manufacturer products. For newer windows
with built-in weatherstripping that has lost its
effectiveness over time, pry out a sample and take
it to the window manufacturer or supplier for
replacement with the same type. Cheaper products
are usually less durable and less effective, so do not
choose merely on the basis of cost.
Preparation and installation are important and
typically involve the following steps:
ry to adjust and square windows that are out
• T
of alignment.
• R
emove old weatherstripping, caulking and blobs
of paint from contact surfaces. If the surface
is very uneven, apply a bead of caulking under
the weatherstripping or fill, sand and paint the
surface to make it smooth.
lean the surface with a clean cloth and
• C
fast-drying mineral spirits or MEK (methyl
ethyl ketone).
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Keeping the Heat In ● Upgrading windows and doors
• A
pply the weatherstripping. With doors and
windows that are used often, you may want to
reinforce the adhesive types with staples.
window. You can do a better job if you first remove
the stop and the bottom sash.
• C
heck the window for smooth operation and
ensure all hinges, slides and hardware operate
freely and correctly.
Top
Weatherstrip the space where the two sashes meet by
removing the lower sash and applying V-type weatherstripping to the upper window from the inside.
• Periodically check the weatherstripping for wear.
i) Double-hung and single-hung windows
Double-hung and single-hung windows should be
weatherstripped on the sides, top and bottom of the
moving sash, as shown in Figure 8-5. Caulk air leaks
around the fixed portion of the window.
Sides
The thin plastic V-type weatherstripping is a good
choice. Open the window and slip the stripping up
the crack between the sash and the frame, with the
mouth of the V facing the exterior. It need only
extend to 25 mm (1 in.) above the top of the closed
Figure 8-5 Where to weatherstrip a single-hung
window
Bottom
Apply V-type or compression-type neoprene rubber
to the windowsill where the closed window will sit
or to the bottom of the moving window sash itself.
ii) Sliding windows
Sliding windows with sashes typically use brush
weatherstripping that will require removing the sash
and pulling the old weatherstripping out of its slot.
Cut the new material to the length required and
snap or slide it into the slot. Tack, staple or glue
each end of the brush material to ensure that the
Figure 8-6 Brush weatherstripping on a sliding
window
Weatherstrip the
side of the sash
V-strip
Weatherstrip
the upper and
lower sashes
INSIDE
INSIDE
ENT
M
OVE
M
SASH
V-strip
Sash
Weatherstrip
the sill
V-strip
Brush-type weatherstripping
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Keeping the Heat In ● Upgrading windows and doors
weatherstripping stays in place before reinstalling
the sash.
Sashless sliders – panes of glass not encased in a
frame – are inefficient. At the very least they should
be supplemented with interior storm windows.
Better yet, replace them with energy-efficient units.
iii) Swing-type (hinged) windows
Swing-type (hinged) windows are treated like doors.
Apply weatherstripping to the frame so it meets
the edge of the sash or place it on the stop where
it will meet the face of the sash. The force of a
closed window against the weatherstripping makes
a pressure seal. Hinged windows usually require
a combination of V-strip and compression-type
weatherstripping. Hinges and locking hardware
may complicate the job. Sometimes, more than one
weatherstrip will therefore be needed in those areas.
Figure 8-7 Compression and sweep
weatherstripping on a casement
window
INSIDE
SA
SH
M
OV
EM
ENT
Sweep-type
weatherstripping
Compression-type
weatherstripping
8.1.7 Storm window systems
Single-glazed windows lose about 10 to 20 times as
much heat as the same area of a properly insulated
wall. Storm windows or double-glazed sealed units
will reduce the heat loss by almost half.
Storm windows can be installed on the inside or the
outside, can be permanent or seasonal, and can be
made to order.
Exterior storm window systems
Exterior storm windows were once very common
and continue to serve a useful role in many
applications. They are usually constructed of a
wood or metal frame, with glass or an acrylic sheet
as glazing.
Exterior storm windows can be either seasonal
(installed in the fall and removed in the spring) or
permanent. Seasonal storm windows should be
inspected each year before installation to ensure
that the glazing, putty and weatherstripping are in
good condition. A drawback of seasonal units is
the labour involved in installing and removing them
each year, as well as the need for storage. Permanent
exterior storm windows are usually equipped with a
built-in screen and a sliding sash.
When you use exterior storm windows, the main
interior window must be air sealed more tightly than
the storm window to prevent moist household air
from entering the space between the windows and
being trapped, where it can condense and cause
deterioration of the sash and frame.
Interior storm window systems
Interior storm windows are generally attached
directly to the window frame, which helps reduce
air leakage around the window. To minimize
condensation and air leakage, interior storm
windows should be sealed tightly so that no warm
air gets between the storm unit and the original
window after installation.
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Keeping the Heat In ● Upgrading windows and doors
Interior storm windows are lighter and more
accessible than seasonal exterior storm windows
especially on upper floors. A disadvantage is that
blinds or other window treatments may have to be
repositioned to accommodate the storm window.
Interior storm windows are typically used in the
winter only and are stored for the rest of the year.
However, in an air-conditioned house, they can also
help keep heat out and cool air in during the hot
summer months.
There are two common interior storm window
system options – heat-shrink film with doublesided tape and clear rigid acrylic sheets with
magnetic seals.
i) Heat-shrink film with double-sided tape
These inexpensive, temporary, do-it-yourself kits
are sold at most hardware and building supply
stores and include instructions for installation. With
this system, two-sided tape attaches the film to the
window trim, after which the film is heated with a
hair dryer to shrink it tightly across the window. In
most cases, the film can be used only once.
Although this system provides an excellent seal and
good visibility, the two-sided tape can lift paint when
it is removed. As well, once this system is installed,
the window cannot be opened without removing or
puncturing the film.
Points to keep in mind:
ightweight film may be damaged if you have
• L
young children or pets in the house.
• P
lastics must be kept away from strong heat
sources.
• S ome people may be sensitive to plastics, which
can emit odours, particularly when their surfaces
are warmed by sunlight.
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ii) Clear rigid acrylic sheets with magnetic seals
This seasonal system is more durable than plastic
film but more expensive; plus, it may require the
services of a contractor. To install a magnetic seal
system, a metal strip is fastened to the window trim
using double-sided tape (this strip can be painted
to match the frame). A magnetic moulding is then
secured to the acrylic sheet and the sheet is pressed
into place on the metal strip.
When the acrylic sheets are not in use, they must be
stored in a flat or vertical position (not slanted) and
in a cool place protected from exposure to sunlight
and excessive heat. The rigid glazing is easier to
clean and has a more finished appearance than
shrink film.
Some plastic supply stores sell these systems
(and the appropriate cleaning products) and can
cut the sheets to the size required. As well, some
firms specialize in manufacturing and installing
these systems.
Specialty products
There are two products that are most suitable for
areas that have very high solar gains that make
the room too hot: applied window films and
multi-layered polyester films. Films are usually
professionally applied with some precautions.
Applied window films are usually made from a clear
or tinted polyester substrate with a scratch-resistant
coating on one side and an adhesive with a protective
liner on the other. Multi-layered polyester films are
black on one side and silver on the other. The film
is permanently attached to the window by removing
the liner and pressing it firmly on the glass.
Window films with a solar-control coating reduce
solar gain and help protect carpeting, draperies,
furniture and wood from fading. They should not
be used on all windows as they offer very little
increased insulation and greatly cut down on solar
gain, which could lead to higher energy bills during
Keeping the Heat In ● Upgrading windows and doors
the heating season. There is also a small risk of glass
breakage due to increased thermal stress and the use
of these films may void the warranty issued by the
original window manufacturer.
Curtains and blinds can help reduce radiant heat loss
from windows during the heating season and reduce
solar gain during the summer. Shutters, shades,
awnings and trees can also reduce solar gains during
the summer. Close window coverings during the day
and open windows at night for ventilation.
During the heating season, insulated drapes offer
somewhat more benefit than non-insulated drapes
and blinds. However, as curtains and blinds are
not airtight, they may cause window condensation
problems in the winter.
8.1.8 Skylights
Skylights commonly suffer from water leakage and
condensation around the frame and curb or tunnel.
For operable skylights, ensure that hardware is
working and all seals are in good order. Keep rain
out by repairing exterior seals and flashings. Curbs
and interior tunnels around the skylight must be
well insulated and air sealed to reduce condensation.
Reduce summer overheating with light-reflective
glazing and blinds.
Do not open a skylight (or upper storey window) in
hot weather if the house air temperature is cooler
than the outside air. Opening the skylight draws hot
air into the house, negating the effectiveness of air
conditioning or natural cooling.
8.1.9 Information on buying new windows
and doors
Helpful publications include Consumer’s Guide to
Buying Energy-Efficient Windows and Doors and EnergyEfficient Residential Windows, Doors and Skylights. See
the “Resources” chapter for information on how to
obtain these booklets.
8.2 DOORS
Poor installation, years of hard use, shifting
foundations and seasonal warping can often force
hinged doors and sliding glass patio doors to
become out of square with their frames. If doors
do not fit snugly, fix or replace the door, frame,
hardware, gaskets and weatherstripping. The same
techniques for preparing windows (as explained in
Section 8.1, Windows) apply to all doors including
any needed repairs or adjustments, surface
preparation and cleaning for the weatherstripping.
Figure 8-8 Methods of weatherstripping a door
A) Weatherstripping
the face of the door
B) Weatherstripping
the edge of the door
C) Weatherstripping the
bottom of the door
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Keeping the Heat In ● Upgrading windows and doors
Weatherstrip the top and sides of the door
frame as illustrated in Figure 8-8, Part A and
Figure 8-8, Part B. The easiest and most effective
weatherstripping for a door frame is a good quality
V-shaped vinyl type. It makes contact with the edge
of the door and provides a good seal even when the
door warps from season to season.
For increased protection, attach weatherstripping
to the stop so that it presses against the face of the
door as shown in Figure 8-8, Part A.
There are also many types of combination metal
and foam or rubber weatherstripping that are
screwed to the stop. They should be adjusted
regularly to conform to the changing warp of
the door.
Apply weatherstripping to either the door sill (see
the threshold in Figure 8-8, Part C) or to the door
itself. Although this can be a difficult area to seal
well, it is worthwhile doing because this is often
a source of major drafts. Use durable material
that can withstand traffic and is flexible enough
to conform to changes in the door caused by
fluctuations in humidity and temperature. The
weatherstripping should also be easy to replace.
A good seal can usually be obtained with gasketed
door-bottom weatherstripping that attaches
to the door, or with full or partial threshold
weatherstripping that is attached to the door sill.
When the weatherstripping is applied to the door
itself, a very durable material is necessary. The most
effective choice is the combination type, which is
simply tacked or screwed along the bottom inside
surface of the door. There should be slots that allow
for some adjustment of the weatherstripping.
There is a wide variety of door weatherstripping
on the market, including kits that include
weatherstripping and threshold or door bottom
seals. Some products come with replacement seals.
Look for high-quality, durable products.
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For sliding patio doors, replace weatherstripping
and hardware when worn. Replace poor condition
sliding patio doors with ENERGY STAR® qualified
units or with French or garden-style doors and
additional energy-efficient windows. In the interim,
older patio sliding doors not used in winter can be
sealed with removable sealant or covered with heatshrink film.
8.2.1 Contracting the work
Air sealing and repairing windows and doors
can become part of the work of an air sealing
contractor (see Chapter 3, “Materials”). If you
are having only some of the windows or doors
replaced, ask the contractor to check and replace
defective weatherstripping on the remaining units.
8.2.2 Window and door contractors
When getting estimates, make sure the contractor
has experience in the type of work you want done.
Ask the contractor if the company offers a thirdparty warranty on products and services.